What is a periglacial environment?
exist at the edges of glacial / polar environments and cover 20% of earth’s land surface
what are the three characteristics of periglacial environments?
1) Found on the edges of glacial / polar environments - alaska / russia / Northern Europe
2) No permanent covering of ice - do experience cold for most of year (frost) with periodic snow
3) Permafrost is one key feature of periglacial environments
Whats the permafrost?
Where a layer of sediment, soil or rock below the ground remains frozen for 1 year+
Whats the active layer?
The layer above the permafrost that thaws in summer and refreezes again in winter.
What is a talik?
A layer of unfrozen ground that is surrounded by permafrost due to anomaly in thermal conditions.
What is continuous permafrost?
A continuous sheet of frozen material which extends without any breaks→ found in Siberia Russia - higher latitudes
What is discontinuous permafrost?
Is permafrost that is broken up into separate areas → Hudson bay Canada - warmer regions
What is sporadic permafrost?
- Found when mean annual temperature is just below 0
the summer temperatures reach several degrees above
isolated pockets of permanently frozen ground remain below the surface.
Lower latitudes - prevent complete thawing
What is frost action ?
- Leads to the accumulation of angular rocks at the foot of a mountain slopes or a boulder strewn landscapes
- Cracks in the ground formed by winter contraction become filled with water during the day
- Water freezes and expands - enlarges the crack
- Over many years an ice wedge is formed up to 3m x 10m
What is a soliflucation?
- The water in the upper active layer melts leading to soil becoming saturated
- If on a slope causes the downhill movement of top layer of soil under force of gravityAKA Gelifluction
rockfalls
- Result from freeze thaw action
- Scree slopes are a common feature of periglacial environments
- On flat land extensive areas of angular boulders can be left known as block fields
Nivation
Snow collects in hollows especially on north facing slopes
With increase amount of weight if the ice begins to disintegrate the underlying rock
Frost Heave
A subsurface process that leads to vertical sorting of material in the active layer.
- Stones within finer material heat up and cool down faster than their surroundings as have lower heat capacity
- Temperatures fall water beneath the stones freeze and expand pushing the stones upwards to the surface
- Ground ice also pushes up finer material
- Warm season → thawing causes ice to convert back to water and the contracting surface drops particles in elevation → this is influenced by gravity causing for particles to move downslope
